Relationships between Soil Parameters and the Growth of Wheat Plants on an Acid Soil in Rwanda

Three wheat categories with different biomass production were studied on tropical Inceptisols in Rwanda. Growth parameters such as number of tillers per square meter, average plant height, and shoot and root biomass were determined, and elemental concentrations of roots and leaves measured. In order to identify reasons for inhibited wheat growth soil parameters such as pH, exchangeable cations, C_org and N_tot were determined. As aluminum toxicity was suspected on the acid soils, aluminum fractionation was carried out in water extracts of the soil samples using 8-hydroxyquinoline. Growth parameters correlated well with exchangeable aluminum and with soil pH. These findings, along with root morphology, indicated aluminum toxicity at the low productivity plots. Aluminum fractionation results strengthened this hypothesis, but did not give much additional information. The reasons for this are discussed. Simultaneously, the elemental concentrations of the leaves suggested Ca, Mg and P deficiencies.